YPVS TUNING

TZ 350 G Hitachi, Femsa & Motoplat ignitions improve performance a lot but don’t generate electricity for your lights so are no good for road bikes .After market pipes will also give a good power boost. Some will just move the power around not actually give more B.H.P .Tel your tuner what pipes you are using so he can match the tune to the pipes .Otherwise you could get a top end screamer that doesn’t work below 10,000 rpm grate fun ok for the track but useless for the road and hard on the pistons and rings .

Yamaha saw fit to give the early YPVS a horribly under sprung, poorly damped, non-rebuild able rear shock. This can still be said of the latest Brazilian model, though the FII are a little better. Despite wider, air-assisted fork tubes then the deposed LC’s the YPVS front end is still too soft for hard use.

Using tapered roller head bearings is a must and improve the front end a lot ,as will adding a steering damper even a cheep one will do . I found doing both of these things improved the front end of my FII a lot .

Experience gained from the pro-am {YPVS only} and marl borough championships led to the development of the Hegira spax shock at around £250. It has adjustable pre load and rebound damping with a choice of springs .

Fork conversion kits to improve damping and spring rate rate including springs and oil seals will cost around £160 .Maxton do the Maxton Koni shock with damp and rebound adjustment for the rear .

The carbs, pipes & ignition are the biggest restrictive on any LC or YPVS .The best standard carbs are the FI YPVS 26mm’s . TZR or RD 400 E 28mm’s are more then adequate for most road tuned bikes .I used the RD 28mm’s on my yammagamma . TZ 36mm power-jet carbs are my choice for a fully tuned YPVS’s

skimming the head raises the compression and does improve performance even on a standard engine, making it slightly peaker . the heads shown here have been made like this for easy maintience on a tuned motor .

Hear are two YPVS barrels, the one on the left tuned the other standard, you can clearly see the difference. At least I hope so when I fit them to my latest project

The YPVS has a bridged inlet port allowing a more tuned inlet area then the LC without the piston slapping. The big end rollers and con rods are 1mm wider, giving the crank a longer life.RD500 big end’s are the same size as the YPVS but have an extra roller in so are a good choice for a tuned bike .

The 83 YPVS peaked at 9.500 rpm, but the FI revised exhausts moved this up to 10.000rpm. then Yamaha ruined it with the FII’s restrictive carbs, ignition & exhausts brining it down to 8.500rpm. The FII is less prone to seizures and the pipes do look loads better then the earlier ones

Most people would be shocked at the true B.H.P of their bikes .You could get a good 10 B.H.P difference from one dino to another on the same day. They all seem to be set up different and all swear theirs is right, but how can they all be right?. Most tuners would agree a road tune gives 10% power gain and a fast road tune 25% power gain. A proddy tune 35% power gain, still more from 2mm oversize pistons. Remember more power equals less reliability and more maintenance. The bikes also become more sensitive to hotter, cooler & damp days sometimes changing dramatically the way they perform or not as the case may be , especially if you have S&B,K&N or similar air filters .